Abstract Photolysis of paramethyl benzyl manganese pentacarbonyl (CO)5Mn-p-CH2C6H4CH3 (4a)and paramethoxy benzyl manganese pentacarbonyl (CO)5Mn-p-CH2C6H4OCH3(4b) with 1-2 equivalents of R3SiH in C6H6 or C6D6 at 5℃ yields the silyl manganese pentacarbonyls (CO)5MnSiR3 [SiR3 = SiMe2Ph (1b), SiMePh2 (1c), SiPh3 (1d), SiHPh2 (1e), SiEt3 (1f), SiMe2tBu(1g), and SiMe2Et (1h) ] in moderate to high yields after chromatographic purification. Quantitative production of respective byproducts p-xylene and p-methylanisole, along with variable yields of Mn2(CO)10 (<1 % to 6 %) are observed after the photochemical reaction. Conditions for the chromatographic isolation differ for each product. Choice of column size and temperature (room temperature to - 65 ℃) is made according to initial concentration-dependent decomposition (overloading), stability during development and separability of 1 with Mn2(CO)10. Once freed from Mn2(CO)10 1b - 1g were isolated as pale yellow oil or off white crystals (only 3h was not isolated pure). Although very air sensitive these products are otherwise stable thermally.

Key words: photochemical synthesis, silyl manganese pentacarbonyl, variable temperature chromatographic isolation